MIX cornstarch, broth, soy, brown sugar, garlic and ginger in saucepan. Cook and stir until mixture boils and thickens.
THREAD alternately pork, mushrooms and onion on 4 long skewers.
GRILL or broil kabobs 20 minutes or until done, turning and brushing often with broth mixture. Place a tomato on each skewer.
HEAT remaining broth mixture to a boil. Serve with kabobs and rice.